The invention relates to an energy delivery system for performing myocardial revascularization on a beating heart of a patient.
Transmyocardial revascularization (TMR) is a surgical treatment for cardiovascular disease. Present TMR procedure is an open chest technique (thoracotomy) that uses a laser beam to drill holes through the myocardium, typically into the left ventricle. These holes or channels extend through the entire heart wall thickness from the outside through to the ventricle. The openings of the channels on the outside surface of the heart heal due to external pressure from the surgeon, but the channels are believed to remain open on the inside, allowing blood to enter the heart wall tissue from the ventricle.
In another approach myocardial revascularization can be performed using a catheter introduced percutaneously so that the tip of the catheter is inside a chamber of the heart, typically the left ventricle, where the holes or channels can be created from the inside toward but not through the outside of the heart. This approach is also known as endocardial laser revascularization (ELR), percutaneous myocardial revascularization (PMR), and direct myocardial revascularization (DMR). The channels are drilled with a laser beam introduced through the catheter.
Certain problems are presented when laser revascularization is done on a beating heart. A beating heart presents a moving target, which can make it difficult to accurately and consistently form channels of a desired depth and size. The heart also is extremely sensitive to a laser pulse at certain times during its cycle. A laser pulse striking the heart at the T time of an electrocardiogram (ECG) signal could cause the heart to fibrillate and result in heart failure. While one could stop the heart during the process of TMR, this poses other risks to the patient and complicates the operating procedure. The heart must be cooled and the patient connected to a heart-lung machine.
However, the risk of inducing a beating heart to fibrillate is greatly reduced when the laser is fired only during the refractory period of the heart cycle between the R and T waves of the ECG signal. An additional benefit of firing the laser only between the R and T waves is that this is the period of the heartbeat cycle during which the heart is most still and channels can be formed most accurately. Rudko U.S. Pat. No. 5,125,926 describes a heart-synchronized pulsed laser system that fires a laser only during the refractory period of the heartbeat cycle. The patent describes an open chest procedure using an articulated optical arm or a fiber optic element to deliver the laser beam to a surface of the heart.
Aita U.S. Pat. No. 5,389,096 discloses a percutaneous TMR procedure in which a steerable heart catheter is guided from the femoral artery via the abdominal artery into the left ventricle. The laser energy is delivered through the working channel of the catheter by a fiber optic delivery system.
WO 98/27877 and Eggers U.S. Pat. No. 5,860,951 describe using electrical current pulses delivered from electrodes on a catheter (for percutaneous access) or handpiece (for external access) to create channels in a TMR procedure.
The above-referenced patents and PCT publication are hereby incorporated by reference in their entireties.